Green DJ, Westhead EW, Langley KH, Sattelle DB. Aggregation and dispersity of isolated chromaffin granules studied by intensity fluctuation spectroscopy.
BIOCHIMICA ET BIOPHYSICA ACTA 1978;
539:364-71. [PMID:
630006 DOI:
10.1016/0304-4165(78)90040-5]
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Abstract
The aggregation and dispersity of isolated bovine adrenal secretory vesicles (chromaffin granules) were studied by intensity fluctuation spectroscopy. The degree of dispersity and the Z-average translational diffusion coefficients were calculated from the autocorrelation functions of the intensity fluctuations in laser light scattered from the granules in solution. Granules purified by sedimentation through 0.3 M sucrose/Ficoll/2H2O showed greater dispersity than granules purified by sedimentation through 1.6 M sucrose. By monitoring the scattered light intensity and the diffusion coefficients of the granules, many of the difficulties encountered in the interpretation of absorbance measurements were avoided. Measurements over a range of granule concentrations in sucrose solutions (10 mM HERPES, pH 7.0), indicated that aggregation of the granules occurred at concentrations above 150 microgram protein/ml. At low granule concentrations (15-30 microgram protein/ml) Ca2+-induced aggregation was detected at a threshold of 2-10 mM calcium.
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